Explosives and propellants are often confined in munitions. When exposed to inadvertent events such as extreme heat, bullet impact, fragment impact, shape charge impact, or nearby munition explosions, the energetic materials may be initiated inadvertently. Such inadvertent initiations usually cause catastrophic explosions impacting persons, property, environment, and frequently cause damage to or loss of other nearby weapons, including due to fratricidal action.
Insensitive munitions may instead reduce the severity of reactions to external stimulus by various methods. One method is to minimize confinement of the energetics comprising propellants or explosives, e.g., so that the energetics will burn instead of detonate if totally confined. A way to do this in a conventional confined munition is to include vents in the munition for expansion of burning gases. Thereby the energetics will not be absolutely confined and cause an explosion. Most energetic materials outgas and expand during heating, causing an increase in pressure. However, the gases causing this pressure are sometimes unable to reach the desired vents to relieve this pressure, or the vents may have been plugged up, though such vents may indeed have been initially provided. Despite provision of these vents in such cases one could still have the unwanted explosions due to confinement.
An improved approach according to this invention is to always specifically include a melt able inert liner material between the metal casing and the energetic. The object is to take up space with the liner material where this space might be later used to lessen the confinement above mentioned, if the liner material's space could be freed away when it is needed for expansion. In this case, if the liner melts as planned, that would provide a pathway to relieve pressure imparted onto the energetic by confinement.
One problem involved in fabricating and providing such liners is that munitions often have small mouth openings that prevent a liner from being fabricated outside of the munition and then later inserted. This might seem to limit the usage of insensitive munitions liners for these applications.
Another approach might be to insert rigid pre-fabricated sleeves into an existing munition. A warhead might be redesigned to enlarge the openings into the munition solely to allow insertion of the pre-fabricated sleeve. Then, the smaller opening to the munition could be restored by then adding additional metal parts to recreate a small mouth opening for the munition. A problem with the above is that changing the size of the metal part opening often changes the weight, interfaces, and lethality profile of a munition. The approach is also costly. It is also difficult to retrofit already existing manufactured parts, and to do so with dependable consistency.